Advanced space missions using nanosatellite constellations are hindered by a lack of miniaturized low power attitude determination and control systems. Replacing large conventional spacecraft attitude sensors with smaller low power sun sensors is desirable for both three axis stabilized spacecraft and spinning spacecraft. A three axis stabilized spacecraft may have a centroid sun sensor having a central detector pointing at the sun with a series of circumferentially disposed detectors surrounding the central detector for determining when the sun is off center of a pointing line of sight when pointing directly towards the sun. An optical lens is used to focus the received sun light onto the central detector. A spinning spacecraft uses a scanning sun sensor that necessary scans a field of view for determining when the sun is in-view by creating an intensity profile where the maximum intensity points to the sun along a line of sight for determining the location of the sun and relating the location of the sun to the spin phase of the spacecraft for attitude determination. The sun sensor on the spinning spacecraft also has multiple detectors for providing an elevation angle relative to a spin intensity bit map profile for indicating the spinning phase and the sun elevation angle. The scanning sun sensor also has a lens for focusing the received sun light onto the sensor. In both the centroid sun sensor and the scanning sun sensor, the received sun light passes directly through a viewing port having a band limited filter, a lens for focusing the light on a detector that may be, as examples, a single pixel, a linear array, a circular array, or a matrix array of photodetectors. These conventional sun sensors are well suited for sun sensing. However, these conventional sun sensors do not sweep the field-of-view for creating a two-dimensional bit map of the sky, which may enhance attitude determination with interpolations.
In general, sun sensors should have low-mass, low power usage, and low volume with accurate and wide spatial coverage. For nanosatellite and microsatellite applications, smaller and lower power sun sensors can be made using advanced semiconductor processing. Imaging systems have used readout chips with photodiode detectors to collect received light and to channelize bit image information. These imaging systems have also used discrete lenses for focusing the image onto the photodetectors. These imaging systems, such as a imaging camera, have a CMOS active pixel array upon which is focused the received light. The availability of submicron CMOS technology, the maturity of CMOS fabrication methods, and the advent of low noise active pixel sensors have enabled high performance CMOS digital imager developments. The primary advantages of a CMOS based design are random access, lower power usage, digital interfacing, simplicity of operation using a single CMOS compatible power supply, high speed, miniaturization through system integration, on-chip signal processing circuits, and radiation tolerance. However, existing sun sensors are relatively large and consume high power. These and other disadvantages are solved or reduced using the invention.